Make the function signature less prominent, add an early example to docs

Signed-off-by: Nick Cameron <nrc@ncameron.org>

docs/kcl-std/functions/std-assert.md

@@ -8,20 +8,23 @@ layout: manual
 Check a value meets some expected conditions at runtime. Program terminates with an error if conditions aren't met. If you provide multiple conditions, they will all be checked and all must be met.
 
 ```kcl
+n = 10
+assert(n, isEqualTo = 10)
 assert(
-  @actual: number,
-  isGreaterThan?: number,
-  isLessThan?: number,
-  isGreaterThanOrEqual?: number,
-  isLessThanOrEqual?: number,
-  isEqualTo?: number,
-  tolerance?: number,
-  error?: string,
+  n,
+  isGreaterThanOrEqual = 0,
+  isLessThan = 100,
+  error = "number should be between 0 and 100",
 )
+assert(
+  1.0000000000012,
+  isEqualTo = 1,
+  tolerance = 0.0001,
+  error = "number should be almost exactly 1",
+)
+
 ```
 
-
-
 ### Arguments
 
 | Name | Type | Description | Required |
@@ -36,6 +39,21 @@ assert(
 | `error` | [`string`](/docs/kcl-std/types/std-types-string) | If the value was false, the program will terminate with this error message | No |
 
 
+### Function signature
+
+```kcl
+assert(
+  @actual: number,
+  isGreaterThan?: number,
+  isLessThan?: number,
+  isGreaterThanOrEqual?: number,
+  isLessThanOrEqual?: number,
+  isEqualTo?: number,
+  tolerance?: number,
+  error?: string,
+)
+```
+
 ### Examples
 
 ```kcl